Blasting mats, typically made of portions of used vehicle tires held together by cables or other similar elements, are designed to limit the movement of ground (i.e., rock fragments, and soil) at a ground surface in response to detonation of an explosive below the ground surface. As is well known in the art, a blasting mat typically is positioned at a particular location for a blast, and then removed after the blast, and moved to another location, for use in connection with another detonation. The conventional blasting mat may be any suitable size, e.g., approximately 10 feet by 15 feet.
Accordingly, the weight of the blasting mat should be as low as possible, because of the need to move the blasting mat after each use. However, the typical blasting mat should also have sufficient weight to achieve an effective blanketing effect over the ground surface, to limit movement of portions of the ground surface in response to the detonation.
In general, substantially the same types of materials (e.g., portions of used vehicle tires) typically are used throughout the blasting mat. However, depending on the density of the material and the manner in which the blasting mat is used, this uniformity may result in unnecessary costs being incurred, e.g., in connection with the purchase of the materials, or in the costs incurred in handling the blasting mat.
For the purposes hereof, an “automobile tire” is understood to be a “PLT” (passenger and light truck tire), as the term was used under the Ontario Tire Stewardship Program (OTSP). It will therefore be understood that the “automobile” tire may be a tire for a passenger vehicle, or for a light truck (a pickup truck, or an SUV). In addition, for the purposes hereof, a “truck tire” is understood to be a “MTT” (medium truck tire), as the term was used in the OTSP. Accordingly, for the purposes hereof, the “truck” for which a “truck tire” is made is a transport truck.
The conventional method of forming a portion of a used automobile tire for use in a conventional blasting mat is as follows. As can be seen in FIG. 1A, a used automobile tire 10 typically is cut along a longitudinal center line 12 into two halves, identified in FIG. 1A by reference characters “A1” and “A2” for convenience. Conventionally, each of the two halves is then further divided into three substantially equal portions. For example, as illustrated in FIG. 1B, the used automobile tire half “A1” is further divided into three substantially equal portions 14. Typically, in order to form a prior art blasting mat, the used automobile tire portions 14 are arranged in rows “R”, each of the rows generally being parallel to other similar rows of used automobile tire portions (not shown in FIG. 1B).
For clarity of illustration, three used automobile tire portions in one row are identified in FIG. 1C by reference characters 14A, 14B, 14C, and three used automobile tire portions in an adjacent row are identified by reference characters 14D, 14E, and 14F. As can be seen in FIG. 1C, to form a conventional blasting mat, the used automobile tire portions typically are arranged on a generally flat surface in rows with alternating orientations, the used automobile tires each defining a “u” in one row that is oriented in an opposite direction relative to the used automobile tire portion(s) in the row beside it. There is some overlap of the tire portions. It will be understood that the used automobile tire portions 14, as illustrated in FIG. 1C, are each conventionally positioned in the row on the flat surface on the longitudinally cut edge of the tread part (i.e., as cut along center line 12), with a sidewall part 15 thereof (FIG. 1B) facing upwardly, and a tread part 16 (FIG. 1A) located substantially vertical. Typically, a number of parallel rows are arranged in this way, to form an uncompressed body. The used automobile tire portions are connected together by generally horizontally-positioned cables (not shown in FIGS. 1A-1C) drawn through holes formed in the used automobile tire portions.
The automobile tire portions 14, thus arranged into several parallel rows, are then compressed to form the prior art blasting mat (not shown). The automobile tire portions are held together under such pressure by an arrangement of the cables that are drawn through the automobile tire portions, and by clamps (not shown) on the cables to engage the used automobile tire portions.
Alternatively, the prior art blasting mat may be made of used truck tire portions 17.
In FIG. 1D, the typical used truck tire portion 17 is illustrated. As is well known in the art, the used truck tire portion 17 is a tread part 18 of the used truck tire. Sidewalls of the truck tire (not shown in FIG. 1D) typically are not included in the used truck tire portions 17. Those skilled in the art would appreciate that the tread part is cut from the used truck tire, and the sidewall part of the truck tire may be recycled. The length of each of the tread parts 18 may be any suitable length.
To form a blasting mat of the prior art (not shown), the used truck tire portions may be arranged into rows. Conventionally, the used truck tire portions 17 are positioned on their edges respectively, so that the treads of each are substantially vertical. For clarity of illustration, the used truck tire portions in FIG. 1E arranged on their edges in the row “R” are identified by reference characters 17A, 17B, and 17C. (As will be described, embodiments of the invention are illustrated in the balance of the attached drawings.)
To form a conventional blasting mat using used truck tire portions, a number of parallel rows of used truck tire portions are assembled, cables are drawn through the used truck tire portions, and then the body so assembled is compressed, to form another version of the prior art blasting mat. As in the process of forming the conventional blasting mat that includes portions of used automobile tires, in order to keep the used truck tire portions compressed, suitable clamps are positioned on the cables on one side of the completed body, to hold the used truck tire portions under compression.
Typically, and as described above, the blasting mats of the prior art are made of portions of used automobile tires, or alternatively, they may be made of portions of used truck tires. The prior art blasting mats typically do not include both automobile tire portions and truck tire portions. Also, in the prior art, the blasting mat is conventionally formed by compressing the entire body once, in a horizontal direction, and clamps are secured to the cables, to keep the entire body subjected to the same pressure.
As a result, in the prior art, the typical blasting mat has approximately the same density throughout. However, the typical blasting mat is relatively large, to provide satisfactory protection from the blast. Because of this, the conventional blasting mats are relatively heavy, with the consequence that they are relatively difficult to move, and cumbersome to locate in a preselected location relative to a proposed blast.